The invention relates to a procatalyst for polymerization of olefins. The invention also relates to a process for preparing said procatalyst. Furthermore, the invention is directed to a catalyst system for polymerization of olefins comprising the said procatalyst, a co-catalyst and optionally an external electron donor; a process of preparing polyolefins by contacting an olefin with said catalyst system. The invention also relates to the use of said procatalyst in the polymerization of olefins.
Catalyst systems and their components that are suitable for preparing a polyolefin are generally known. One type of such catalysts are generally referred to as Ziegler-Natta catalysts. The term “Ziegler-Natta” is known in the art and it typically refers to catalyst systems comprising a transition metal-containing solid catalyst compound (also typically referred to as a procatalyst); an organometallic compound (also typically referred to as a co-catalyst) and optionally one or more electron donor compounds (e.g. external electron donors).
The transition metal-containing solid catalyst compound comprises a transition metal halide (e.g. titanium halide, chromium halide, hafnium halide, zirconium halide, vanadium halide) supported on a metal or metalloid compound (e.g. a magnesium compound or a silica compound). An overview of such catalyst types is for example given by T. Pullukat and R. Hoff in Catal. Rev.—Sci. Eng. 41, vol. 3 and 4, 389-438, 1999. The preparation of such a procatalyst is for example disclosed in WO96/32427 A1 and EP 1 086 961.
There is, however, an on-going need in industry for catalysts showing better performance, especially better yield and higher polymer bulk density.
It is thus an object of the invention to provide a procatalyst for polymerization of olefins and a process to prepare such a procatalyst. It is a further object of the present invention is to provide a procatalyst which shows better performance, especially higher yield and higher polymer bulk density.